What I've had happen is that in manual mode with Auto ISO, the camera will occasionally grossly overexpose. Usually it will just be 1 or 2 shots, but yesterday I had a whole series of shots that were way too overexposed. Shooting in very bright sunlight, 1/1000 sec @ f8, the camera set the ISO for one shot to 10,000! It should have been 200. After a dozen or so shots like that, it suddenly straightened itself out and started exposing normally. FYI, I shoot a lot from the hip so I can't check exposure as I'm going. That's why I tend to rely on Auto ISO, although it clearly isn't always dependable. It may be time to go full-on manual and set everything, including the ISO, myself. I do wish that "automatic" was more "automagic!"